3D Engineering Model Retrieval Based on Enhanced Shape Distributions

To reuse and share the valuable knowledge embedded in repositories of engineering models for accelerating the design process, improving product quality, and reducing costs, it is crucial to devise search engines capable of matching 3D models efficiently and effectively. In this paper, an enhanced shape distributions-based technique of using geometrical and topological information to search 3D engineering models represented by polygonal meshes was presented. A simplification method of polygonal meshes was used to simplify engineering model as the pretreatment for generation of sample points. The method of sampling points was improved and a pair of functions that was more sensitive to shape was employed to construct a 2D shape distribution. Experiments were conducted to evaluate the proposed algorithm utilizing the Engineering Shape Benchmark (ESB) database. The experiential results suggest that the search effectiveness is significantly improved by enforcing the simplification and enhanced shape distributions to engineering model retrieval.

Parametric geometry representations for wind turbine blade shapes

Based on the Joukowsky transformation and Theodorsen method, a novel parametric function （shape function） for wind turbine airfoils has been developed. The airfoil design space and shape control equations also have been studied. Results of the analysis of a typical wind turbine airfoil are shown to illustrate the evaluation process and to demonstrate the rate of convergence of the geometric characteristics. The coordinates and aerodynamic performance of approximate airfoils is rapidly close to the baseline airfoil corresponding to increasing orders of polynomial. Comparison of the RFOIL prediction and experimental results for the baseline airfoil generally show good agreement. A universal method for three-dimensional blade integration-＂ Shape function/Distribution function＂ is presented. By changing the parameters of shape function and distribution functions, a three dimensional blade can be designed and then transformed into the physical space in which the actual geometry is defined. Application of this method to a wind turbine blade is presented and the differences of power performance between the represented blade and original one are less than 0. 5%. This method is particularly simple and convenient for bodies of streamline forms.

Development of a mass model in estimating weight-wise particle size distribution using digital image processing

Particle size distribution of coarse aggregates through mechanical sieving gives results in terms of cumu- lative mass percent. But digital image processing generated size distribution of particles, while being fast and accurate, is often expressed in terms of area function or number of particles. In this paper, a mass model is developed which converts the image obtained size distribution to mass-wise distribution, mak- ing it readily comparable to mechanical sieving data. The concept of weight/particle ratio is introduced for mass reconstruction from 2D images of particle aggregates. Using this mass model, the effects of several particle shape parameters （such as major axis, minor axis, and equivalent diameter） on sieve-size of the particles is studied. It is shown that the sieve-size of a particle strongly depend upon the shape param- eters, 91% of its variation being explained by major axis, minor axis, bounding box length and equivalent diameter. Furthermore, minor axis gives an overall accurate estimate of particle sieve-size, error in mean size （D-50） being just 0.4%. However, sieve-size of smaller particles （〈20 ram） strongly depends upon the length of the smaller arm of the bounding box enclosing them and sieve-sizes of larger particles （〉20 mm） are highly correlated to their equivalent diameters. Multiple linear regression analysis has been used to generate overall mass-wise particle size distribution, considering the influences of all these shape parameters on particle sieve-size. Multiple linear regression generated overall mass-wise particle size distribution shows a strong correlation with sieve generated data. The adjusted R-square value of the regression analysis is found to be 99 percent （w.r,t cumulative frequency）. The method proposed in this paper provides a time-efficient way of producing accurate （up to 99%） mass-wise PSD using digital image processing and it can be used effectively to renlace the mechanical sieving.

数据驱动的自动化码头岸桥与AGV

自动化集装箱码头中岸桥和自动引导车(automated guided vehicle,AGV)紧密衔接,需要统筹规划以追求整体最优。为了提高岸桥和AGV作业系统的协同性,提出了一个双层优化模型,同时决策岸桥和AGV的配置与作业顺序。在AGV自动路径寻优模式下,为控制其行驶时间的不确定,本文基于码头历史作业数据,采用分布鲁棒优化方法刻画AGV行驶时间,建立模糊机会约束控制岸桥等待风险,构建数据驱动的双层优化模型并得到等价形式。为求解该模型,基于L-shaped算法框架,设计一种结合模拟退火算法和邻域搜索算法的自适应大邻域搜索算法求解。实验结果表明:本文模型算法能够有效提高岸桥和AGV调度的协同性,成功解决实际作业规模案例,提升整体运输体系效能。

Hierarchical 3D mechanical parts matching based-on adjustable geometry and topology similarity measurements

A hierarchical scheme of feature-based model similarity measurement was proposed,named CSG_D2,in which both geometry similarity and topology similarity were applied.The features of 3D mechanical part were constructed by a series of primitive features with tree structure,as a form of constructive solid geometry(CSG) tree.The D2 shape distributions of these features were extracted for geometry similarity measurement,and the pose vector and non-disappeared proportion of each leaf node were gained for topology similarity measurement.Based on these,the dissimilarity between the query and the candidate was accessed by level-by-level CSG tree comparisons.With the adjustable weights,our scheme satisfies different comparison emphasis on the geometry or topology similarity.The assessment results from CSG_D2 demonstrate more discriminative than those from D2 in the analysis of precision-recall and similarity matrix.Finally,an experimental search engine is applied for mechanical parts reuse by using CSG_D2,which is convenient for the mechanical design process.

Measurement, modelling, and closed-loop control of crystal shape distribution： Literature review and future perspectives

Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too challenging to achieve automatic closed-loop control. Previous work has focused on controlling the crystal size distribution, where the size of a crystal is often defined as the diameter of a sphere that has the same volume as the crystal. This paper reviews the new advances in morphological population balance models for modelling and simulating the crystal shape distribution （CShD）, measuring and estimating crystal facet growth kinetics, and two- and three-dimensional imaging for on-line characterisation of the crystal morphology and CShD. A framework is presented that integrates the various components to achieve the ultimate objective of model-based closed-loop control of the CShD. The knowledge gaps and challenges that require further research are also identified.

User controllable anisotropic shape distribution on 3D meshes

This paper presents an automatic method for computing an anisotropic 2D shape distribution on an arbitrary 2-manifold mesh. Our method allows the user to specify the direction as well as the density of the distribution. Using a pre-computed lookup table, our method can efficiently detect collision among the shapes to be distributed on the 3D mesh. In contrast to existing approaches, which usually assume the 2D objects are isotropic and have simple geometry,our method works for complex 2D objects and can guarantee the distribution is conflict-free, which is a critical constraint in many applications. It is able to compute multi-class shape distributions in parallel.Our method does not require global parameterization of the input 3D mesh. Instead, it computes local parameterizations on the fly using geodesic polar coordinates. Thanks to a recent breakthrough in geodesic computation, the local parameterization can be computed at low cost. As a result, our method can be applied to models with complicated geometry and topology. Experimental results on a wide range of3 D models and 2D anisotropic shapes demonstrate the good performance and effectiveness of our method.

考虑工时不确定性的混流U型装配线平衡的分布鲁棒优化方法

在以人工装配为主的流水线生产中,工时的不确定性是影响生产节拍的重要因素。考虑到随机优化要求精确的概率分布信息和较高的鲁棒优化保守性,本文针对工时不确定条件下混流U型装配线平衡问题,采用以经验分布为中心、Wasserstein距离为半径的模糊集对工时的不确定性进行描述,并以最小化生产节拍为优化目标,建立装配线平衡问题的分布鲁棒优化模型。为了降低模型的复杂性,利用强对偶理论将模型转换为易于求解的形式;为保证解的鲁棒性,设计了一种鲁棒性指标并将其作为模型的约束条件。针对上述模型,通过设计一种基于区间数的解码方式,并引入自适应交叉和变异概率,给出了一种改进的遗传算法。最后通过标准算例和断路器抽架生产实例进行了数值仿真实验,结果表明相较于随机优化和鲁棒优化方法,所建立模型在降低结果保守性的同时保持较高的鲁棒性,并且针对问题所提出的改进遗传算法具有良好的寻优能力。

Wages and Salaries of Czech Men and Women at the Beginning of the Third Millennium and the Impact of the Economical Recession on Their Development

This paper deals with the development of the wage distribution in the Czech Republic since 2003, according to gender. It is a development of descriptive characteristics of location, differentiation and shape of wage distribution, but also the development of concentration characteristic of wage distribution. Gross monthly wage of Czech employees represents the variable under research. Emphasis is placed on changes in the development of wage distribution since 2009 in connection with the onset of economic recession. The economic crisis has greatly influenced the development of the wage distribution in the Czech Republic, wage growth virtually stopped at this time. Differences in the development of wage distribution between men and women in the Czech Republic are also under this research. Development of wage distribution has been studied by modelling the distribution. Three-parametric lognormal curves are served as a theoretical probability distribution whose parameters were estimated using the L-moment method of point estimate of parameters. Dependence of gross monthly wage on gender has been the subject of research as well. This dependence was researched using one-way analysis of variance. Forecast of wage distribution of men and women in the Czech Republic for the years 2012 and 2013 is included in this research.

Aerosol structure and vertical distribution in a multi-source dust region

The vertical distribution of aerosols was directly observed under various atmospheric conditions in the free troposphere using surface micro-pulse lidar （MPL4） at the Zhangye Station （39.08°N, 100.27°E） in western China in the spring of 2008. The study shows that the aerosol distribution over Zhangye can be vertically classified into upper, middle and lower layers with altitudes of 4.5 to 9 km, 2.5 to 4.5 kin, and less than 2.5 km, respectively. The aerosol in the upper layer originated from the external sources at higher altitude regions, from far desert regions upwind of Zhangye or transported from higher atmospheric layers by free convection, and the altitude of this aerosol layer decreased with time; the aerosols in the middle and lower layers originated from both external and local sources. The aerosol extinction coefficients in the upper and lower layers decreased with altitude, whereas the coefficient in the middle layer changed only slightly, which suggests that aerosol mixing occurs in the middle layer. The distribution of aerosols with altitude has three features： a single peak that forms under stable atmospheric conditions, an exponential decrease with altitude that occurs under unstable atmospheric conditions, and slight change in the mixed layer. Due to the impact of the top of the atmospheric boundary layer, the diurnal variation in the aerosol extinction coefficient has a single peak, which is higher in the afternoon and lower in the morning.

ON DISTRIBUTED H^(1) SHAPE GRADIENT FLOWS IN OPTIMAL SHAPE DESIGN OF STOKES FLOWS:CONVERGENCE ANALYSIS AND NUMERICAL APPLICATIONS

We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is used for discretizations of distributed and boundary H^(1) shape gradient flows.Convergence analysis with a priori error estimates is provided under general and different regularity assumptions.We investigate the performances of shape gradient descent algorithms for energy dissipation minimization and obstacle flow.Numerical comparisons in 2D and 3D show that the distributed H1 shape gradient flow is more accurate than the popular boundary type.The corresponding distributed shape gradient algorithm is more effective.